High-frequency amplifier

Abstract

Input matching is achieved for a high-frequency range having a center frequency of 0.8 GHz by a capacitor and a coil in an input matching circuit, and input matching is achieved for a high-frequency range having a center frequency of 1.9 GHz by another coil in the input matching circuit. Output matching is achieved for a high-frequency range having a center frequency of 0.8 GHz by a capacitor and a coil in an output matching circuit, and output matching is achieved for a high-frequency range having a center frequency of 1.9 GHz by another coil in the output matching circuit.

What is claimed is: 
     
       1. A high-frequency amplifier for matching both a lower-band high-frequency signal and a higher-band high-frequency signal, comprising: an amplifying circuit having an input and an output;   an input circuit and an output circuit;   an input matching circuit connected between the input of said amplifying circuit and the input circuit; and   an output matching circuit connected between the output of said amplifying circuit and the output circuit,   wherein said input circuit includes an input terminal, an input coupling capacitor connected in series between said input terminal and said input matching circuit,   wherein said input matching circuit includes an input matching capacitor connected to said input circuit, said input matching capacitor being separate from said input coupling capacitor, a first inductor connected between said input matching capacitor and said amplifying circuit, and a second inductor connected to the connection point of said capacitor and said first inductor,   wherein said input matching capacitor and said second inductor form a lower-band frequency matching circuit for achieving matching for a lower-band high-frequency signal, and   said first inductor forms a higher-band frequency matching circuit for achieving matching for a higher-band high-frequency signal which is higher in frequency than said lower-band high-frequency signal.   
     
     
       2. A high-frequency amplifier according to claim 1, wherein the inductance of said second inductor in said input matching circuit is such that said second inductor is open for said higher-band high-frequency signal when said second inductor is viewed from the connection point of said input matching capacitor and said first inductor in said input matching circuit, the capacitance of said input matching capacitor in said input matching circuit is such that matching is achieved for said lower-band high-frequency signal, and   the inductance of said first inductor in said input matching circuit is such that matching is achieved for said higher-band high-frequency signal.   
     
     
       3. A high-frequency amplifier for matching both a lower-band high-frequency signal and a higher-band high-frequency signal comprising: an amplifying circuit having an input and an output;   an input circuit and an output circuit;   an input matching circuit connected between the input of said amplifying circuit and the input circuit; and   an output matching circuit connected between the output of said amplifying circuit and the output circuit,   wherein said output circuit includes an output terminal, an output coupling capacitor connected in series between said output terminal and said output matching circuit,   wherein said output matching circuit includes a first inductor connected to the output of said amplifying circuit, an output matching capacitor connected between said first inductor and said output circuit, said output matching capacitor being separate from said output coupling capacitor, and a second inductor connected to the connection point of said first inductor and said output matching capacitor,   said output matching capacitor and said second inductor form a lower-band frequency matching circuit for achieving matching for a lower-band high-frequency signal, and   said first inductor forms a higher-band frequency matching circuit for achieving matching for a higher-band high-frequency signal which is higher in frequency than said lower-band high-frequency signal.   
     
     
       4. A high-frequency amplifier according to claim 3, wherein the inductance of said second inductor in said output matching circuit is such that said second inductor is open for said higher-band high-frequency signal when said second inductor is viewed from the connection point of said output matching capacitor and said first inductor in said output matching circuit, the capacitance of said output matching capacitor in said output matching circuit is such that matching is achieved for said lower-band high-frequency signal, and the inductance of said first inductor in said output matching circuit is such that matching is achieved for said higher-band high-frequency signal.   
     
     
       5. A high-frequency amplifier according to any one of claims 1, 2, 3, and 4, wherein said amplifying circuit includes:   an input transistor having a control terminal and first and second main terminals, of which the control terminal is connected to the output of said input matching circuit and the first terminal is connected to ground,   an output transistor having a control terminal and first and second main terminals, of which the first terminal is connected to the second terminal of said input transistor and the second terminal is connected to the input of the output matching circuit, and   a voltage source connected to the control terminal of said output transistor for applying a voltage to the control terminal of said output transistor,   wherein said voltage source changes a voltage applied to the control terminal of said output transistor according to the frequency of a high-frequency signal amplified by said amplifying circuit for matching both said lower-band high-frequency signal and said higher-band high-frequency signal.   
     
     
       6. A high-frequency amplifier according to claim 5, wherein said voltage source in said amplifying circuit applies a predetermined voltage to the control terminal of said output transistor such that a minimum input reflection coefficient and a minimum output reflection coefficient are obtained for said higher-band high-frequency signal when said higher-band high-frequency signal is amplified, and applies a predetermined voltage to the control terminal of said output transistor such that a minimum input reflection coefficient and a minimum output reflection coefficient are obtained for said lower-band high-frequency signal when said lower-band high-frequency signal is amplified. 
     
     
       7. A high-frequency amplifier according to claim 5, wherein an impedance circuit is provided between said input transistor and said output transistor in said amplifying circuit. 
     
     
       8. A high-frequency amplifier according to claim 7, wherein said impedance circuit is formed of an inductor. 
     
     
       9. A high-frequency amplifier according to claim 8, wherein said input transistor and said output transistor in said amplifying circuit are field effect transistors. 
     
     
       10. A high-frequency amplifier according to claim 6, wherein an impedance circuit is provided between said input transistor and said output transistor in said amplifying circuit. 
     
     
       11. A high-frequency amplifier according to claim 10, wherein said impedance circuit is formed of an inductor. 
     
     
       12. A high-frequency amplifier according to claim 11, wherein said input transistor and said output transistor in said amplifying circuit are field effect transistors. 
     
     
       13. A high-frequency amplifier according to claim 7, wherein said input transistor and said output transistor in said amplifying circuit are field effect transistors. 
     
     
       14. A high-frequency amplifier according to claim 6, wherein said input transistor and said output transistor in said amplifying circuit are field effect transistors. 
     
     
       15. A high-frequency amplifier according to claim 5, wherein said input transistor and said output transistor in said amplifying circuit are field effect transistors.